The present application relates to a signal value holding apparatus, a signal value holding method, a signal value control system, a signal value control method, a playback apparatus, and a playback method.
An automatic gain control (AGC) is used in a large variety of technical fields today. The AGC is used to maintain substantially constant signal value of an output signal, regardless of the signal value of an input signal. For example, although a received field intensity in a receiving device varies in the wireless communication field, the use of the AGC eliminates the negative effect of the variation of the received field intensity.
The AGC generally includes a variable gain amplifier (VGA) that adjusts the signal value of an input signal and outputs it, a peak hold circuit that evaluates the signal value of the signal supplied from the VGA, a control section that controls the VGA based on the signal value evaluated by the peak hold circuit, and so on. Thus, in order to enhance the performance of the AGC, the response of the peak hold circuit, which is an example of a signal value holding apparatus, is an important factor.
For example, as disclosed in Japanese Unexamined Patent Application Publication No. 11-148950, the peak hold circuit holds the peak value of an input signal at a prescribed droop rate, and, upon input of a signal value larger than the held peak value, updates the held peak value to the input signal value. The droop rate indicates quickness to decrease the held signal value. Thus, one approach to improve the response to an input signal with a decreasing signal value in the peak hold circuit is to increase the droop rate.